There exist many examples of devices that detect the presence or absence of a liquid in a fixed optical arrangement in which the liquid flows through or comes in contact with the apparatus. The liquid is detected by means of optical absorption or reflection, conductivity, physical displacement, ultrasonic, and or capacitive means, but none of which are suitable for use with colorimeters, spectrophotometers, or other optical measuring devices without additional cost and or complexity. More specifically a need exists for the automatic measure of the transmittance of light through a sample wherein a removable vessel contains a biologically active pathogen or toxic substance. It is often desirable to measure the concentration of such hazardous materials without manual manipulation of the controls of the measuring apparatus so as to prevent contamination or contaminate transfer from one operator to another via the apparatus controls.
A unique aspect of the present invention is that a single optical path is used for the detection and measure of the sample concentration. Prior art inventions such as that of Harklau, U.S. Pat. No. 3,923,403, and Briggs, U.S. Pat. No. 4,077,724, measure optical density but do not sense presence of the liquid nor automatically measure the optical density. Prior inventions such as Bilstad et al., U.S. Pat. No. 4,333,016, Zeitz, U.S. Pat. No. 4,631,529, Lavin, U.S. Pat. No. 4,816,695, and Kraft et al., U.S. Pat. No. 5,508,521 measure presence of a liquid but are unable to measure the density of the detected liquid due to limitations of the optical systems employed. Prior art Boullet et al., U.S. Pat. No. 4,779,462 does automatic measurement of mud in a liquid, but does so by utilization of separate detection and measurement means, as of conductivity of the liquid and displacement—not using a direct optical measure of the light absorption by the liquid.
An objective of the present invention is to provide an automatic means to initiate a measurement cycle in a optical density meter, colorimeter, or spectrophotometer upon insertion or extraction of a sample or vessel (vial, cuvette, test tube, or the like), in order to eliminate cross-contamination of the measurement device with biologically active pathogens or toxic substance that may be present on the surfaces of the sample.
An automatic measurement that is controlled according to the insertion and removal of does not requiring physical contact with the controls of the device in order to initiate a measurement cycle, thus improving measurement efficiency and reducing the number of contacts and steps required by the operator in order to perform an optical measurement.
Another objective of an automatic means is that the automatic measurement cycle be configurable as continuous, discrete, or for a sequence of measures, for the duration of the presence of the sample within the measurement apparatus.
It is also an objective of the invention to eliminate the need for a separate means for the initiation of the measurement cycle from that of the means used for the measurement.
It is also an objective of the invention that the automatic means be repetitive, requiring no additional action other than removal of the vial or cuvette from the device in order to prepare the device for the next vial insertion initiated measurement cycle.
Still another objective of the invention is prevent contamination and intrusion of the internal workings of the apparatus that cannot be easily disinfected or reached, or would otherwise adversely effect the operation of the apparatus in the event of a spillage of a content of the vial; (i.e., spillage of a biologically active pathogens or toxic substance is contained to external surfaces of the apparatus).
It is a further objective of the present invention that the automatic measurement means maintains readiness with minimal power consumption so as to be useful for long periods of time as in battery-powered applications.